Chapter 27—Prokaryotes

Archaebacteria&

Bacteria

Classification• Old 5 Kingdom system

• Monera, Protists, Plants, Fungi, Animals

• New 3 Domain system

– reflects a greater

understanding of evolution & molecular evidence

• Prokaryote: Bacteria

• Prokaryote: Archaebacteria

• Eukaryotes

– Protists

– Plants

– Fungi

– Animals

Prokaryote

Eukaryote

Kingdom

Protist

Kingdom

Fungi

Kingdom

Plant

Kingdom

Animal

Kingdom

Archaebacteria

Kingdom

Bacteria

Prokaryotes

Domain Bacteria

Domain Archaea

DomainBacteria

DomainArchaea

DomainEukarya

Common ancestor

Bacteria live EVERYWHERE!

• Bacteria live in all ecosystems

– on plants & animals

– in plants & animals

– in the soil

– in depths of the oceans

– in extreme cold

– in extreme hot

– in extreme salt

– on the living

– on the dead

Bacterial diversity

rods and spheres and spirals… Oh My!

Prokaryote Structure

• Unicellular

– bacilli, cocci, spirilli

• Size

– 1/10 size of eukaryote cell

• 1 micron (1um)

• Internal structure

– no internal compartments

• no membrane-bound organelles

• only ribosomes

– circular chromosome, naked DNA

• not wrapped around proteins

prokaryotecell

eukaryote cell

Prokaryote vs. Eukaryote

Chromosome

double helix

Prokaryote

Eukaryote

Variations in Cell Interior

internal membranesfor photosynthesislike a chloroplast

(thylakoids)

internal membranesfor photosynthesislike a chloroplast

(thylakoids)

internal membranes

for respiration

like a mitochondrion

(cristae)

internal membranes

for respiration

like a mitochondrion

(cristae)

aerobic bacterium

mitochondria

cyanobacterium(photosythetic) bacterium

chloroplast

Prokaryote Cell Wall Structure

peptide sidechains

cell wallpeptidoglycan

plasma membrane

protein

Gram-positive bacteria

Gram-negative bacteria

peptidoglycan

plasmamembrane

outermembrane

outer membrane of lipopolysaccharides

cell wall

peptidoglycan = polysaccharides + amino acid chains

lipopolysaccharides = lipids + polysaccharides

Prokaryotic metabolism

• How do bacteria acquire their energy & nutrients?– photoautotrophs

• photosynthetic bacteria

– chemoautotrophs• oxidize inorganic compounds

– nitrogen, sulfur, hydrogen…

– heterotrophs• live on plant & animal matter

• decomposers & pathogens

Genetic variation in bacteria

• Mutations

– bacteria can reproduce every 20 minutes

• binary fission

– error rate in copying DNA

• 1 in every 200 bacteria has a mutation

• you have billions of E. coli in your gut!

– lots of mutation potential!

• Genetic recombination

– bacteria swap genes

• plasmids

– small supplemental

circles of DNA

• conjugation

– direct transfer of DNAconjugation

Bacteria as pathogens

• Disease-causing microbes

– plant diseases

• wilts, fruit rot, blights

– animal diseases

• tooth decay, ulcers

• anthrax, botulism

• plague, leprosy, “flesh-eating” disease

• STDs: gonorrhea, chlamydia

• typhoid, cholera

• TB, pneumonia

• lyme disease

Bacteria as beneficial (&

necessary)• Life on Earth is dependent on bacteria

– decomposers

• recycling of nutrients from dead to living

– nitrogen fixation

• only organisms that can fix N from atmosphere

– needed for synthesis of proteins & nucleic acids

– plant root nodules

– help in digestion (E. coli)

• digest cellulose for herbivores

– cellulase enzyme

• produce vitamins K & B12 for humans

– produce foods & medicines

• from yogurt to insulin